Preservation of urine specimens

ABSTRACT

A liquid urine preservative comprised of boric acid and alkali formate dissolved in a bacteriostatic liquid, such as water or glycerine. The preservative may be included in an evacuated container for a urine sample to facilitate taking of correct sample amounts.

This is a division of application Ser. No. 3,234, filed Jan. 15, 1979,now U.S. Pat. No. 4,258,032 issued Mar. 24, 1981.

This invention relates to the preservation of urine specimens.

Bacterial quantitation of clean-voided urine specimens is employed todetermine the presence of urinary tract infection. In many cases,however, such specimens are contaminated from exogenous sources, and inview of the fact that urine has the capability of supporting theproliferation of bacteria, multiplication of such contaminants may occurwhile will result in false positives. As a result, in order to preventmultiplication of contaminants, culturing or refrigeration of a urinespecimen within two to four hours is recommended. In many cases,however, such culturing or refrigeration is not possible, and as aresult, there is a need for a preservative for urine specimens which iscapable of preserving the urine to prevent multiplication of bacterialcontaminants.

Powdered boric acid has been proposed as such a preservative; however,it has been found that such powdered boric acid is toxic to some of thetest strains present in the urine. In addition, such powdered boric acidis not effective for preventing proliferation of some bacterialcontaminant strains.

As a result, there is a need for an effective preservative for urinespecimens.

In accordance with the present invention, there is provided a liquidpreservative for urine specimens comprised of boric acid and alkaliformate dissolved in a bacteriostatic liquid. Such boric acid and alkaliformate are dissolved in the bacteriostatic liquid in an amounteffective to preserve a urine specimen. Applicant has found that such aliquid preservative is effective for preserving a urine specimen for aperiod of at least 24 hours, and in most cases, such preservative iscapable of preserving a urine specimen for a period of 48 hours. Thus,applicant has found that the liquid preservative in accordance with thepresent invention prevents undue proliferation of bacterialcontaminants, and is also not unduly toxic to bacteria present in thespecimen.

The boric acid is generally present in the liquid preservative in anamount to provide a boric acid concentration in the urine sample in theorder of from 0.9 to 1.2 per cent. The alkali formate is generallypresent in the preservative in an amount to provide a formateconcentration in the urine sample of from 0.5 to 0.6 percent. The alkaliformate is generally either potassium or sodium formate.

The bacteriostatic liquid employed in the preservative is generallyeither water or glycerine, with glycerine being preferred in that boricacid is more soluble in glycerine, thereby permitting the use of smalleramounts of the total liquid preservative per unit of sample. Inaddition, it has been found that glycerine interacts with the boric acidand formate to provide for increased preservation; i.e., a liquidpreservative in accordance with the invention which includes glycerineas the bacteriostatic liquid has been found to be an effectivepreservative for a period of 48 hours.

In accordance with a preferred embodiment of the present invention, theliquid preservative is included in a sample container for a urinesample; in particular, an evacuated container, such as an evacuatedtube, as described in U.S. Pat. No. 2,460,641. In this manner, theevacuated container includes an amount of liquid preservative effectivefor preserving the predetermined amount of urine sample which will bedrawn into the evacuated sample container. This facilitates handling ofthe sample, and provides for an effective amount of preservativetherefor.

The invention will be further described with respect to the followingexample; however, the scope of the invention is not to be limitedthereby:

EXAMPLE

Urine samples were preserved as follows:

A. Prior Art - Boric Acid

Urine sample containing 1% of Boric Acid.

B. Prior Art - Boric Acid

Urine sample containing 1.8% Boric Acid.

C. Present Invention

Boric Acid and sodium formate dissolved in glycerine and added to urinesample to provide 1% boric acid; 0.5% sodium formate; and 10% glycerinein urine.

Each of the preserved urine specimens were tested for its effectivenessagainst bacteriuria samples by diluting 0.1 ml of the sample with 9.9 mlof sterile distilled water, with 0.1 ml of the diluted sample beingtransferred to culture plates for count determination after 0.24 and 48hours.

The preservation ability is evaluated by determining whether there is anunacceptable rise or drop in the bacterial count, either of whichindicates that the preservation is ineffective. The results were asfollows:

    ______________________________________                                        1.  E. Coli                                                                       Composition A - Unacceptable drop in count after 24 hours.                    Composition B - Unacceptable drop in count after 48 hours.                    Composition C - Suitable.                                                 2.  C. Freundii                                                                   Composition A - Unacceptable increase in count after                          48 hours.                                                                     Composition B - Unacceptable drop in count after 24 hours.                    Composition C - Suitable.                                                 3.  S. Pyogenes                                                                   Composition A - Unacceptable drop after 24 hours.                             Composition B - Unacceptable drop after 24 hours.                             Composition C - Suitable.                                                 4.  S. Faecalis - Composition A - Unacceptable rise after 24 hours.               Composition B - Unacceptable rise after 48 hours.                             Composition C - Slight and acceptable rise after 48 hours.                5.  P. Mirabilis                                                                  Composition A - Suitable                                                      Composition B - Unacceptable drop after 48 hours.                             Composition C - Suitable.                                                 6.  P. Morgani                                                                    Composition A - Suitable                                                      Composition B - Unacceptable drop after 48 hours.                             Composition C - Suitable.                                                 7.  Pseudomonas                                                                   Composition A - Suitable                                                      Composition B - Unacceptable                                                  Composition C - Suitable                                                  ______________________________________                                    

All three compositions were found to be suitable as a preservative forE. Cloacac; and K. Pneumoniae.

The composition of the present invention (Composition C) was also foundto be comparable to a urine sample preserved by refrigeration over the24 hours and 48 hour test periods.

A composition in accordance with the invention using water as thebacteriostatic liquid (concentration in urine 1% boric acid; 0.5 sodiumformate; 50% water) was found to be an effective preservative in theabove tests over the 24 hour period. In some cases, after 48 hours,preservation was not effective.

The present invention is particularly advantageous in that it has beenfound that by employing the preservative of the present invention forpreserving urine samples, the urine preservation is favorably comparableto that obtained by refrigeration. As a result, by proceeding inaccodance with the present invention, it is not necessary to effectrefrigeration of a urine sample. Moreover, the present invention offersthe advantage that urine preservation can be effected with small amountsof preservative, thereby eliminating the necessity of employing adilution actor in the sample determination. Furthermore, by providingsuch a preservative in an evacuated container, handling is eased and acorrect amount of preservative is added to a predetermined quantity ofurine sample. Thus, for example, in accordance with a preferredembodiment, it is possible to employ 0.5 ml of a preservative comprisedof boric acid and sodium formate dissolved in glycerine in accordancewith the invention in a tube evacuated to draw 5.0 ml of a urinespecimen. The preservative is preferably formulated to provide 1% boricacid and 0.5% sodium formate in the urine sample.

As shown in the drawing, in accordance with a preferred embodiment, hereis provided an evacuated tube 10 closed by stopper 12, which includes apreservative 11 in accordance with the invention. The preservative 11 isincluded in an amount to preserve the sample quantity which will bedrawn into the tube upon piercing stopper 12. A urine sample can betransferred to tube 10 as known in the art by piercing stopper 12 with acannula. A sample cup for facilitating such introduction is disclosed inU.S. application Ser. No. 859,591, filed on Dec. 12, 1977 now U.S. Pat.No. 4,116,066 issued Sept. 26, 1978.

These and other advantages should be apparent to those skilled in theart from the teachings herein.

Numerous modifications and variations of the present invention arepossible in light of the above teachings and, therefore, within thescope of the appended claims, the invention may be practised otherwisethan as particularly described.

In the claims:
 1. A sample device for urine, comprising:an evacuatedsample container for urine and a bacteriostatic liquid preservative forurine in said evacuated sample device, said liquid preservativecomprising boric acid, alkali formate and a liquid selected from thegroup consisting of water and glycerine in amounts effective to providea liquid preservative for a urine sample, said boric acid and alkaliformate being dissolved in the liquid to provide from 0.9 to 1.2% ofboric acid and from 0.5 to 0.6% of alkali formate in a urine sample. 2.The device of claim 1 wherein the liquid is water.
 3. The device ofclaim 1 wherein the liquid is glycerine.
 4. The device of claim 3.wherein the formate is sodium formate.
 5. The device of claim 4, whereinthe boric acid and formate are present in the glycerine in an amount toprovide about 1% boric acid, 0.5% sodium formate and 10% glycerine in aurine sample.
 6. The device of claim 5 wherein the evacuated containeris evacuated to draw a 5.0 milliliter urine sample and contains 0.5milliliters of the liquid preservative.